Pain and Analgesics Flashcards
What is pain?
The subjective conscious appreciation of a stimulus causing or threatening tissue damage.
What is nociception?
Th physical process of detecting and transmitting noxious stimuli.
What are nociceptors?
Sensory receptors that detect noxious stimuli, often located in free nerve endings.
What are the two types of nociceptive fibres?
Aδ fibers (sharp pain) and C fibers (dull, aching pain).
What receptor is activated by heat, protons, and capsaicin in nociceptors?
TRPV-1 (Vanilloid receptor 1)
What is hyperalgesia?
An increased response to a noxious stimulus.
What is allodynia?
A painful response to a normally non-noxious stimulus.
What neurotransmitters are involved in nociceptive transmission at the spinal level?
Glutamate, Substance P, and CGRP (Calcitonin Gene-Related Peptide).
What are AMPA and NMDA receptors?
Glutamate receptors involved in fast (AMPA) and slow (NMDA) excitatory postsynaptic potentials (EPSPs).
What is the “wind-up” phenomenon in pain?
Repeated stimulation of nociceptors causing increased spinal neuron excitability, leading to central sensitisation.
What are the primary endogenous opioids?
Endorphins, enkephalins, and dynorphins.
What are the three main opioid receptros?
μ (mu), κ (kappa), and δ (delta)
What are the effects of μ-opioid receptor activation?
Analgesia, euphoria, respiratory depression and constipation.
How do NSAIDs reduce pain?
By inhibiting cyclooxygenase (COX) enzymes, decreasing prostaglandin synthesis.
What are COX-1 and COX-2 enzymes?
COX-1 is involved in protective functions (e.g. gastric mucosa), while COX-2 is induced during inflammation.
What is neuropathic pain?
Pain arising from nerve damage or dysfunction, often unresponsive to opioids/NSAIDs.
What drugs are used for neuropathic pain?
Tricyclic antidepressants, antiepileptic drugs (e.g., gabapentin), and topical capsaicin
What is the WHO pain ladder?
A framework for pain management:
- Mild pain: NSAIDs.
- Moderate pain: Weak opioids (e.g., codeine).
Severe pain: Strong opioids (e.g., morphine).
What are the major adverse effects of opioids?
Respiratory depression, constipation, tolerance, dependence and sedation
What is Substance P?
A neuropeptide involved in transmitting pain signals via NK-1 receptors.
What role does the periaqueductal gray (PAG) play in pain modulation?
It is a key site in the descending pain pathway that reduces nociceptive transmission.
How do cannabinoids relieve pain?
By acting on cannabinoid receptors to reduce nociceptive signalling.
What is central sensitisation?
Increased excitability of spinal neurons, amplifying pain responses.
What are common undesirable effects of NSAIDs?
Gastric irritation, kidney disorders and increased cardiovascular risk (with COX-2 inhibitors).
